From the CO2Science archive: Deteriorating climates, brought on by cooling temperatures, reduce the carrying capacity of agrarian lands. Consequently, they often deprive the human population of sufficient food; and, if severe enough, can lead to the unavoidable consequence of a population collapse. The latest study to demonstrate as much comes from the research team of Jia et al. (2018), who analyzed “how the spatiotemporal distribution of archaeological settlements was influenced by temperature changes and social factors during the last millennium” in northeast China.

Paper reviewed: Jia, D., Li, Y. and Fang, X. 2018. Complexity of factors influencing the spatiotemporal distribution of archaeological settlements in northeast China over the past millennium. Quaternary Research 89: 413-424.

Their analysis covered the period AD 961 to 1911, which included two dynasties during the warm climate of the Medieval Warm Period (Liao and Jin) and three dynasties during the cold period of the Little Ice Age (Yuan, Ming and Qing).

Using archaeological settlement data from historical records on regional development, Jia et al. found there were a whopping 3,457 and 3,437 settlements in northeast China as far north as 47° latitude during the Liao (AD 916-1125) and Jin (AD 1115-1234) dynasties of the Medieval Warm Period (MWP), respectively. These settlements were able to exist, in their words, because “the warm climate of the MWP provided a background to promote the positive policies of the Liao and Jin dynasties for the development of agriculture and settlement. In contrast, the number of settlements “declined drastically” as temperatures cooled during the Little Ice Age (LIA), numbering only 78 during the Yuan Dynasty (1279-1368), 101 during the Ming Dynasty (1368-1644) and 134 during the Qing Dynasty (1644-1911). Agriculture during the LIA was almost nonexistent; and the settlements retreated by as much as 3 to 4 degrees of latitude below their MWP locations.

Clearly, as illustrated in the data presented above, warming and warmer times are associated with good times for humanity, as exemplified by the greater numbers of settlements the land of northeast China was able to support under such climatic conditions, while cooling and colder times were typically just the opposite, with many significant settlement collapses.